Unjoin geometry of structural foundation

Hi everyone, I’m trying to unjoin about 140 instances of a structural foundation element that is cutting the foundation concrete beams. The command in revit is easy, I just have to unjoin geometry by only clicking once in the instance, without having to second select the beam that is being cut.
I´m, using the next scheme to do the work, but I´m not getting any results. I guess it´s a very easy solution but I´m new to dynamo and can`t work it out.

Thanks a lot.

Well it seems there is a workaround. You have to suppose that dynamo only unjoins two elements and that the command does not work for a “one click” unjoin variation.

So,with this assumption, if you make a list of two selections of family type like in the attached image, it works correctly.